Electric signaling apparatus



(No Model.) 4 Sheets-Sheet 1.

W. W. HIBBARD. ELECTRIC SIGNALING APPARATUS.

Patented July 17, 1894'.

(No Model.) 4 Sheets-Sheet 2.

W.'W. HIBBARD. A

ELECTRIC SIGNALING APPARATUS. No. 523,121. Patented July 17, 1894.

(No Modl.) :4'SheetsSheet a.

W. W. HIBBARD.

ELECTRIC SIGNALING APPARATUS. No. 523,121. Patented July 17, 1894.

(No Model.) 4 SheetsSheet 4.

W. W. HIBBARD. ELECTRIC SIGNALING APPARATUS.

No. 523,121. Patented July 17,1894.

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NORRIS PETERS ca, womu na. WASHINGTON. n. c,

WILLIAM W. HIBBARD, OF ROCHESTER, NEW'YORK, ASSIGNOR TO THE STANDARDELECTRIC SIGNAL COMPANY, OF SAME PLACE.

ELECTRIC SIGNALING APPARATUS."

SPECIFICATION forming part of Letters Patent No. 523,121, dated July 17,1894:. Application filed August 12,1893. Serial No. 483,023. (No model.)

To all whom it may concern.-

Be it known that I, WILLIAM W. HIBBARD, of Rochester, in the county ofMonroe and State of New York, have invented a certain new and usefulImprovement in Electric Signaling Apparatus; and I do hereby declarethat the following is a full, clear, and exact description of the same,reference being had to the drawings accompanying this application.

This improvement relates to electric signals, more particularly firealarm signals, and consists of a system embodying a main line providedwith suitable signal boxes, said main line being normally closed, arelay with subcircuits connecting therewith, a differentiatinginstrument by which the currents through the several subcircuits arechanged, and certain other connecting mechanism which will be more fullydescribed.

In the drawings,Figure 1 is a diagram showing a plan of the system. Fig.2 is a face view of the differentiating instrument with the top removedto show the working parts. Fig.3 is a plan view of the relay. Fig. 4 isa perspective view of the electrical stop apparatus of thedifferentiating instrument. Fig. 5 is a face view of one of the firealarm boxes. Fig. 6 is a similar View with a portion of the top brokenaway to show the interior mechanism. Fig. 7 is a vertical sectionthrough one edge of Figs. 5 and 6 showing the finger knob for startingthe signal apparatus of the fire'alarm box. Fig. 8 is a face view of oneof the police boxes with the top partially broken away. Fig. 9 is a faceview of one of the auxiliary or substation boxes with the top partiallybroken away; Fig. 10 is a section through one edge of the auxiliaryboxes showing the finger knobs for starting the apparatus. Fig. 11 is ahorizontal cross section of Fig. 10.

In this system a central station or office is employed, where arelocated all the workingv house or fire-department station, E a police orother station with which the system is connected, and F a magnet foroperatinga register at the central station, whereon is recorded thenumber of the box where' the alarm is given.

. The relay A is made double where connec tion is made by thesnb-circuits to two difierent .points, say the fire department and thepolice station, and is so shown in the drawings, the same consisting oftwo pairs of electro magnets a a and a a, two sets of uprights e e and ee, two sets of swinging armatures, one set at each end of the relay, andtwo upright contact posts I) and b. The armature at one end of the relayconsists of three arms c 0 attached to a common pivoted bar, the twooutside ones a 0 coming in contact with the uprights e 6 when themagnets are energized, and the middle one o in contact with the uprightpost b in the opposite position. The armature at the opposite end of therelay is of the same construction, consisting ofthe three upright arms ac and c and operate in the same manner.

' The object of the differentiating apparatus B is to change the currentfrom one circuit to another by the rotation of an arm which comessuccessively in contact with different conducting points on an insulatedsurface of the box. It consists of a circular case provided with anexterior face at of rubber or other insulating material, and a metallicbase plate f which acts as a conductor.

g is a time-movement or clock-work of any suitable construction locatedin the case, and h an escapement connected therewith.

c is an arm forming a circuit breaker attached to the time-movement theshaft of said arm extending from the base out through the insulated faceof the instrument, and the arm resting across the same but not incontact therewith. The time movement when released gives motion to thearm and causes it to traverse over the face of the instrument.

is Z Z and m are contact blocks forming electrodes set into theinsulated face of the instrument, and n n are two spring tongues formingcontact points attached to the rotating arm 2', and connected with eachother by a conducting web W, said tongues and their connection loeinginsulated from the arm by a rubber block 0. As the arm rotates thespring tongues come in successive contact with the several conductingblocks 7c 1 Z and m and change the currents, as will be more fullydescribed.

1) p is an electro'magnet within the instrument, and q is a pivotedcrank forming an armature operating in connection therewith. On theouter end of this crank is a pin (1 which passes out through a slot inthe face of the instrument and intercepts a corresponding pin 1' on theunder side of the arm 1', thereby holding said arm against rotation.When magnet 19 pis charged the armature is drawn back removing pin gfrom the path of pin 4' and allowing the swinging arm to rotate by ameans of the time-movement before described.

8 s is another electro-magnet in the instrument, and if an armaturepivoted at t and provided with an inclined lug 25 The armature t ispressed forward by a spring a tightened by a screw c. When the magnet ischarged it overcomes the force of the spring and draws the armatureback.

to is an arm pivoted at 10. connected with the base, its free endengaging with the inclined lug t of the armature t. \Vhen in thisposition the arm to rests in contact with a spring :13 attached to aninsulated block :1 When the armature is drawn back by the magnet the armto frees from contact with the spring and opens the circuit passingtherethrough, and remains open till arm to is struck by a pin ,2 on theshaft of the swinging arm t', which restores it to place by pressing itunder the lug The arm wis drawn from contact with spring as by means ofa coiled springj.

The above described arrangement is for communication with the firedeparment, as will presently be explained.

The same arrangement is duplicated on the opposite side of thedifferentiating instrument B, consisting of the magnets s s, thearmature 6 provided with inclined lug t spring a, screw 1), arm wcontact spring 41: attached to insulated block y, and coiled spring j,the whole operating to establish communication with the policedepartment, or other station than the fire department, as will be morefully described.

The main circuit consists of two wires 1 and 2 laid through the streetsor other locality where the line is to be established, said wires beingprovided with batteries G and H, respectively, at the central station.The terminals of wire 1 connect with the two contact blocks 7t 70' alsoforming electrodes of the differentiating instrument, and the terminalsof wire 2 with the two sets of magnets a a of the relay, as shown in thediagram Fig. 1. All signal boxes and lateral circuits entering buildingsare connected with these main wires. Under normal conditions the circuitthrough the mainline is closed, the magnets of the relay are charged,and the armatures of the relay are drawn back as shown in Figs. 1 and 3.But any opening of the main circuit releases the armatures and allowsthem to be drawn in the opposite direction against the posts I) b, andallows the circuit connected with the central station to come intooperation at the proper time. The circuits are as follows: A circuitextends from battery J through wire 3 to armature c, thence, (when themain circuit has been broken and said armature is in contact with theupright post 1),) through post I), thence through wire 4:, through theregister magnet F, charging same and causing it to operate theregistering appara tus, thence through wire 5 to and through magnet 19 pcharging same, and thence through wire 6, (touching the conducting block1%,) back to battery .I, thus completing the circuit. The energizing ofmagnets 19 1? draws back armature q, removes pin g from the path of pinr, and thereby releases the swinging arm t' and allows it to revolve bymeans of the timemechanism before described. Prior to this time thespring tongues n n have remained in contact with the blocks 7.: 7.2.They now leave said blocks and pass to land m. It should be noted thatthe circuit Jjust described is normally open, and is closed only by theopening of the main circuit, and when the main circuit is again closed,as is done by operating a signal box, the circuit J is again opened andrendered non-operative by reason of the charging of the relay magnets aa. Another circuit extends from battery K at the central station to thefire department. This circuit is from battery K through wire 7, uprighte, armature c wire 8, the magnet at the fire station, and wire 9 back tobattery K. Auxiliary to circuit K is another circuit thus:-from batteryK through wire 7, wire 10, spring an, arm w, the pivot to of said arm toto the metallic base of the dilferentiating instrument, through saidbase, through wire 11, wire 8, the magnet at the fire department, wire(hand back to battery K.

I is a circuit extending from the central station to the police or otherstation independent of the fire department. From battery I the circuitis through wire 12, upright e armature 0 wire 13, the magnet at thepolice station, wire 14, back to battery 1. Auxiliary to this circuit isa circuit from battery I through wire 14, the magnet at the policestation, wire 13, wire 15, spring an, arm 20 the pivot 10 of said arm,through the metallic base of the differentiating instrument, wire 16,and wire 12, back to battery I.

The circuit K and its auxiliary circuit just described are duplicates ofthe circuit I and its auxiliary before described, one circuit and itsauxiliary connecting with the police department and the other circuitand its auxiliary with the fire department.

In the main line circuits 1, 2 are located the various boxes for givingsignals; and from said main line also extend loops into buildings andother localities to be guarded, said loops forming sub-circuits andprovided with thermostats and manual boxes as required. The first actionin opening and then closing the main circuit is tov temporarily closethe local circuit J and thus start the differentiating instrument asbefore described, also operating the register F at the central station,and later recording the number of the box from which the signal is sent,said recording being done by punching holes in a slip of paper or byother means. The movement of the arm '5 now causes the springs n n toleave the blocks is k,which breaks the circuit through wire 1, and tocome in contact with the blocks Zm, thereby forming a new circuit. Thiscircuit is from battery J through wire 8, armature c (then in contactwith the upright of the relay magnet), wire 17, wire 18, magnets s 3,wire 19 to contact block Z, thence through the tongues n n to contactblock m, through wire 6, back to battery J. The result of thus chargingmagnets s s is to draw armature i back and release the spring arm w,allowing the latter to separate from spring x, thus breaking the shuntcircuit that previously existed by contact of the arm with the springand extending through the base of the instrument to wire 11. The furtherprogress of swinging armt' causes spring at to leave block Z,'breakingthe circuit just described, and brings the springs n n in contact withblocks Z m and closes a new circuit from battery J as follows:froinbattery J through leases the pivoted arm 10 from spring as in the samemanner as on the opposite side of the dilferentiating instrument,thereby breaking the shunt circuit that previously existed leading frombattery I through the base of the instrument to wire 16. This shuntcircuit,

together with its companion on the opposite side leading out from thebase of the instrument through wires 11 and 16, will not bereestablished again till arms w and 10 are forced into engagement withthe armatures t and t by the pin a near the end of the rotation ofswinging arm 2'. The condition at this juncture is this: Both of theshunt circuits, one leading to the fire department, the other to thepolice station, are open during the remainder of the rotation of theswinging arm 2' after leaving the contact blocks Z m, and until the pin1" of the swinging arm strikes the pin q of armature q, bringing the armto a stop again. Under such conditions the circuit through the firedepartment is from battery K through wire 7, upright e, armature c c,(then drawn back by the magnets a aand subject to any action of therelay,) wire 8, through the magnet at the fire station, and thencethrough wire 9 back to battery K. At the same time the circuit throughthe police station is from batteryI through Wire 12, upright e, armature0 0 wire 13, through the magnet at the police station, and wire 14 backto battery I. It will be seen that at this juncture the register F, thefire station 0, and

the police station E, are each, through the armature at the relay,rendered susceptible to the operation of 'the relay. Any signaltransmitted over the main line will thus, by closing the circuits at therelay, be transmitted to the central-station register, the fire stationand the police station. But while it is desirable to transmit allsignals coming in from all signaling devices on the main line to thecentral station, the fire station and the police station, it is alsodesirable that no signals, other than those relating to fire alarms,should be repeated to the fire department. To secure this result thevarious signal boxes interposed in the main line are of peculiarconstruction as will be more fully described.

It has already been stated that the main line consists of two wires 1and 2, the first connected with the contact blocks k of thedifierentiatinginstrument, and the other with the relay A at the centralstation.v On this 4 7 signal boxes P for sounding alarms from thestreets to the police office or such other place as may be desired.These various boxes have many parts in common with each other and thedifferentiating instrument before described.

They have, respectively, the swinging arms 11' 11 and the clockworks g gg the same as in the differentiating instrument. The street boxes N andpolice boxes P have respectively contact rims and blocks a a a a and0.20. a a set into the insulated faces of the boxes, the

outer rims a and 0. having breaks 6 and b just in advance of thestarting point of the swinging arms, and the inner blocks a a and d ahaving breaks 6 and b as shown in Figs. 5 and 8, which are face views ofsaid boxes. The auxiliary or substation boxes L have also contact rimsand blocks a a a a. or

0, a a a a 0, arranged in five concentric rings on the insulated face ofthe instrument,

and having various breaks between them, as

shown in the face view, Fig. 9. The electric connections are made withthese contact rims and blocks in each box as will presently bedescribed. Each of the swinging arms 2' and i of the street boxes N P,has two outer spring tongues n n and n a connected together andinsulated from the swinging arm, and an inner separate spring tongue 12,and n in electrical contact with the swinging arm. These three springtongues on the arm of each box rest in line with the three concentricrims of the contact blocks so as to sweep over them. In like manner theswinging arm 2" of boxes L has two pairs of spring tongues 01 ICO IIO

n and n it, the springs of each pair connected together and insulatedfrom the arm, and a single intermediate spring 12 electrically connectedwith the arm. These several spring tongues rest over and come in contactwith the five sets of conducting rims and blocks set into the face ofboxes L. The boxes L, N and P have, respectively, electro-magnets 19 p29 similar to the magnets 19 p of the differentiating instrument B; alsopivoted armatures f f provided with inclined lugs f J, also pivotedcrank arms k h it similar to the crank arm q in the differentiatinginstrument, and carrying stop pins at their outer ends for restrainingthe swinging arms. The energizing of said magnets removes the stop pinsand releases the swinging arms in the same manner as in thediflferentiating instrument. In addition to these features the crankarms h it have intermediate arms 70 k which project inward in suchposition as to be struck by the pin 2', on the shaft of the swingingarm, shortly after starting, to reset the crank arm with the armature.Each of the boxes is also provided with a wheel on the shaft of theswinging arm, against the periphery of which wheel bears a spring 1'pressed up by a screw the object of which is to apply suflicientfriction to the gearing of the clock work to prevent back action of thesame. The exterior rims of the boxes also have circuit breaking notches"0 0 arranged in two series in order to indicate numhers for soundingalarms over the main line. In addition to these devices the boxes arestarted in operation manually by pressing the finger on a knob (Fig. 7)which removes a pin 16 from contact with the end of the swinging arm andreleases the latter. The fingerknob stands a little in the rear of thestoppin on the crank arm h or 71 so that when once released by thepressing of the knob the swinging arm has a small degree of rotarymovement and then is stopped by striking the pin on the crank-arm. Theauxiliary or sub-station boxes L are provided with two finger knobs 25similar to the knobs on the street boxes, by which means the swingingarm has two-stops before reaching the restraining pin on the armature,the object of which will be hereinafter described.

It is the design that should a signal be in the act of transmission froman auxiliary or sub-station box L to the central station, and should astreet station box be operated while said auxiliary or sub-station boxis in operation, the first signal given from the auxiliary box will notbe interfered with, but at the end of the operation of the saidauxiliary box, then the street-box which has in the meantime remained insuspension, will complete its operation automatically. It is also thedesign that should a street box be in operation and a manual box or athermostat in a building be operated, such operation will not start theauxiliary orsub-station box; but when the street box has completed itsoperation then an additional operation of a manual box or thermostatwill operate the auxiliary or substation box. It is also the design thatshould a manual box or a thermostat in the circuit leading to thebuildings protected by the auxiliary box be operated, no other manualbox or thermostat in the same circuit will affect the operation of theauxiliary box started by the first manual box or thermostat. Anotherfunction of the auxiliary or sub-station box L is that, immediatelyafter its time movement begins to operate, it closes a circuit andcharges the magnet of the building gong and causes said gong to ringtill its time movement has run down, thus alarming the inmates of thebuilding. Immediately upon the operation of any one of the signal boxesthe circuit on wire 1 is immediately destroyed and is not restored againunder any circumstances till said signal box has ceased to operate andhas performed its function, at which time the current through wire 1 isrestored again and remains in that condition while the system is normal.The condition of the auxiliary or sub-station box L being normal thecurrent is from battery I-I through wire 1, wire 22, contact block atongues n, it contact block a, wire 23 forming the circuit through thebuilding, block a, tongues n 72 block a wire 24, and wire 1 back tobattery H. To complete the circuit the tongues n 'n' it tact block a,wire 24, and wire 1 back to bat-- tery.

The current through wire 2 is from battery G to the base of theinstrument at 2 thence through the swinging arm t" tongue at, contactblock a", wire 28, and wire 2 back to battery G.

In case wire 23 of the building line is broken the electro-magnet p isenergized, as before described, thus attracting the armature,withdrawing the stop-pin that restrains the swing ing arm, and theswinging arm then commences to traverse the instrument.

For a short period after the commencement of the movement of theswinging arm the currents in both wires 1 and 2 are absolutely broken,and remain so until the swinging arm in its progress brings tongue n incontact of the instrument at a, swinging arm 2', tongue n block at withwhich the tongue is then in contact, wire 29, wire 23, contact block 0.tongues m m, contact block a, wire 31, wire 2, back to battery. In casewire 23 in the building is permanently broken there is no current untilthe further progress of the swinging arm has brought tongues 47, n incontact with the rings a and a In the case of the immediate restoring ofwire 23 the further progress of the swinging arm brings tongue n incontact with block (1 The current is then from battery G, wire 2 tozbaseof the instrument at 2 swinging arm 2'', tongue n block a, wire 30,wire23, block (r tongues 21 and at, block at", (with which n is then 111contact,) wire 31, wire 2, back to battery. This current will energizeany electro receptive devices placed in wire 30. The further progress ofthe swinging arm 41' brings tongues n n in contact with the rings a aFrom this time on during the movement of the swinging arm the circuit inwire 2 is the same whether the wire 23 in the building has been brokenpermanently or has been broken and immediately restored. In either casethe signal will be-transmitted to the central station. But in case'thecircuit has been broken and immediately restored, as by a manual box orthermostat, the signal will be transmitted to the central station andthe fire and police department, while it permanently broken it will betransmitted to the {central station only, thus determining at once whatis the difficulty and avoiding unnecessary alarms. The condition now isthat the tongues n n are in contact with the rings a a, respectively,and progressing around the instrument. The circuit of wire 2 is now asfollows :-from battery G through wire 2, branch wire 61,

ring a, tongues n a, ring a wire 32, and

wire 2 back to battery. Ring a is notched on its face in two series withthe numbers indicating the box, as shown at 0 v As the swinging armprogresses over the face of the instrument tongue 41. engages saidnotches and alternately opens and closes the circuit in a well knownway, thus signaling the number of the box at the central station overwire 2. The further progress of the swinging arm brings tongues 01 n incontact with blocks 0. a; tongue at in contact with block a; and tongue11. in contact with block a. The circuit now in wire 1, which isrestored, is from batteryH to wire 1, wire 33, block a, tongues n n,block a, wire 2 l,wire 1, back to battery. The current through wire 2which has been maintained, is-from battery G through wire 2, base of theinstrument at zflswinging arm 2'', tongue n block 0.", wire 28, wire 2back to battery. There the swinging arm is stopped by the first fingerknob until the line man, having repaired the broken wire 23 through thebuilding, puts the same in condition for further service. The fingerknobs for stopping the swinging arm are simply to enable testing to bemade without sounding an alarm at the central station. After suchtesting has been made the swinging arm is released from the knobs andallowed to move forward to the stop-pin on the end of the cranked arm,when it is ready to be released by the electrical action as beforedescribed. 7

Referring now to the street fire boxes N, in the normal condition theswinging arm 11 is held in a stationary position by the finger. knob 15By pressing on this knob the arm is released and moves forward till itstrikes the stop-pin on the end of crank arm 72. and is held there tillthe magnet 19 is charged, drawing back the armature which holds it.

vIn the normal condition tongue n rests on block a, and tongues n n 011the rings a a The current in wire 1 is as follows:from

battery H to the base of the instrument at a through said base, swingingarm 7?, tongue n .block (1 wire 34, wire 1, back to battery.

The current through wire 2 is from battery G through ring a tongues n a,ring a and wire 2 back to battery- The movement of the swinging arm fromthe finger knob to the holding pin removes tongue n from block a andbrings-it in contact with block a, which forms a new circuit in wire 1as follows: from battery H through wire 1, base of the instrument at 2swinging arm 71 tongue'n block of, wire 36, magnet p energizing same,wire 37, wire 34:, and wire 1 back to battery. The current through wire2 remains the same as before, since the tongues n n have not' left therings a a The charging of magnet p attracts the armature f releasescrank arm 72, removes the stop-pin in advance of the swinging arm andallows said arm to operate. The further progress of swinging arm 2'brings tongue "n over the notch 11 in the outer ring a thereby breakingthe circuit in wire 2 leading to the relay at the central station. Thisstarts the differentiating instrument at the central station, as beforedescribed. The further progress of the swinging arm brings tongues n andn again in contact with rings a a restoring the circuit through wire 2.As the arm progresses the tongue 42 passes over the series of notches vo in ring aialternately opening and closing the circuit and signalingthe number of the box at the central station, and through that to thefire department. N ow while this particular box is in operation asdescribed, should some other box on the= main line be started byreleasing its finger knob holding the swinging arm, said arm of thesecond box could advance no farther than the stop pin controlled by theelectro-magnet, and the current through wire 1 being destroyed saidelectromagnet would not be charged and no action could take place. Itwould so remain until the first box, having completed its signal andrestored the current in wire 1, energized the magnet in the second box,when the stop pin in the second box would be withdrawn allowing thesecond box to give its signal following the other. This is doneautomatically.

The police boxes P are identically of the same construction andoperation as the fire boxes above described, with the exception that thebreak 12 in the outer ring a is of greater length than the correspondingbreak b in the fire boxes. This break If is of such length that thecurrent in wire 2 having been broken and the differentiating instrumentat the central station having been started, the current in wire 2 willremain broken until such time as the swinging arm of the differentiatinginstrument shall have passed the point where the fire department circuitis placed in position to receive signals from wire 2. In such case thesignals given at the police boxes are sent to the central station andfrom there to the police station without being sent into the firedepartment.

By the use of this invention all signals which come to the centralstation are recorded there and are dispatched to the properdestinations, such as the fire department or the police department,automatically and without one interfering with the other. The systemalso insures absolute non-interference of the boxes in sounding two ormore alarms at the same time, and automatically causes the second box togive its signal when the first one has been completed. Furthermore itenables auxiliary or sub-station boxes to be used in connection withlateral loops or circuits through buildings, whereby any opening of athermostat or manual box in said lateral loops will automatically startthe auxiliary box and cause it to send the proper signal to the centralstation, and in case of fire also to the fire department.

Having described my invention I do not claim, in this application, thesystem consisting of the relay, differentiating apparatus circuitsextending to side stations in connection with a main line consisting ofa single wire, as embodied in my pending application, serially numbered483,022. Neither do I claim the construction of the differentiatingapparatus and the various signal boxes shown and described in my otherpending applications, serially numbered respectively 483,024- 483,025and483,026 all filed contemporaneously herewith.

\Vhat I claim as new, and desire by Letters Patent, is

1. The combination of a two wire main circuit, signal boxes attachedthereto, a relay with which the terminals of one of the wires connect, adiiferentiating apparatus provided with electrodeswith which theterminals of the other wire connect, and a circuit connected with therelay controlling the differentiating apparatus, for the purposespecified.

to secure 2. The combination of a main circuit com posed of two wiresprovided with signal boxes, a differentiating apparatus havingelectrical connections with the main circuit, a signal box attached tosaid main circuit, and a lateral circuit extending therefrom providedwith thermostats or manuals, either or both, for the purpose specified.

3. The combination of a main circuit composed of twowires, with signalboxes attached, adifferentiatin g apparatusconnected with the maincircuit, capable when in operation of opening the circuit of one of thewires of the main circuit, thereby arresting the action of one box whileanother is transmitting a signal, for the purpose specified.

4. The combination of a main circuit composed of two wires, adifferentiating apparatus having electrical connection with the maincircuit, a signal box interposed in the main circuit connected with bothwires, a normally closed lateral circuit connected with said box,

provided with thermostats and manuals, either or both, so constructedthat the opening of a thermostat or tripping of a manual will open thecircuit and immediately close it again, thereby re-establishing thecurrent through the lateral circuit and main circuit, for the purposespecified.

5. The combination of a main circuit composed of two wires, signal boxesof different kinds attached, a central ofiice apparatus with which theterminals of one wire connect, a relay with which the terminals of theother wire connect, ,two circuits extending to side stations, and acircuit controlling the action of the central office instrument, soconstructed that a box of either kind will transmit its signal to itsproper station without interference with any other box, for the purposespecified.

6. The combination of a main circuit composed of two wires, with signalboxes attached, a central office apparatus with which the terminals ofone of the wires connect, a relay with which the terminals of the otherwire connect, a circuit controlling the action of said central oificeapparatus, and a circuit extending to a side station, so constructedthat under one condition a signal will be transmitted from the maincircuit over the station circuit and under another condition be arrestedin the central office, for the purpose specified.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

W. W. IIIBBARD.

\Vitncsses:

R. F. Osooon, GEORGE A'. BENTON.

IIo

